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Date: Thu, 10 Oct 2019 20:17:45 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH net 8/9] tcp: annotate sk->sk_sndbuf lockless reads
For the sake of tcp_poll(), there are few places where we fetch
sk->sk_sndbuf while this field can change from IRQ or other cpu.
We need to add READ_ONCE() annotations, and also make sure write
sides use corresponding WRITE_ONCE() to avoid store-tearing.
Note that other transports probably need similar fixes.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/net/sock.h | 18 +++++++++++-------
net/core/filter.c | 3 ++-
net/core/sock.c | 15 +++++++++------
net/ipv4/tcp.c | 2 +-
net/ipv4/tcp_input.c | 3 ++-
5 files changed, 25 insertions(+), 16 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index 79f54e1f88277dc7cc64ca0f35fd5ba869a2f96d..3d1e7502333e7ea0ff866f8982048800193caf33 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -883,7 +883,7 @@ static inline int sk_stream_min_wspace(const struct sock *sk)
static inline int sk_stream_wspace(const struct sock *sk)
{
- return sk->sk_sndbuf - sk->sk_wmem_queued;
+ return READ_ONCE(sk->sk_sndbuf) - sk->sk_wmem_queued;
}
void sk_stream_write_space(struct sock *sk);
@@ -1207,7 +1207,7 @@ static inline void sk_refcnt_debug_release(const struct sock *sk)
static inline bool __sk_stream_memory_free(const struct sock *sk, int wake)
{
- if (sk->sk_wmem_queued >= sk->sk_sndbuf)
+ if (sk->sk_wmem_queued >= READ_ONCE(sk->sk_sndbuf))
return false;
return sk->sk_prot->stream_memory_free ?
@@ -2220,10 +2220,14 @@ static inline void sk_wake_async(const struct sock *sk, int how, int band)
static inline void sk_stream_moderate_sndbuf(struct sock *sk)
{
- if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) {
- sk->sk_sndbuf = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
- sk->sk_sndbuf = max_t(u32, sk->sk_sndbuf, SOCK_MIN_SNDBUF);
- }
+ u32 val;
+
+ if (sk->sk_userlocks & SOCK_SNDBUF_LOCK)
+ return;
+
+ val = min(sk->sk_sndbuf, sk->sk_wmem_queued >> 1);
+
+ WRITE_ONCE(sk->sk_sndbuf, max_t(u32, val, SOCK_MIN_SNDBUF));
}
struct sk_buff *sk_stream_alloc_skb(struct sock *sk, int size, gfp_t gfp,
@@ -2251,7 +2255,7 @@ bool sk_page_frag_refill(struct sock *sk, struct page_frag *pfrag);
*/
static inline bool sock_writeable(const struct sock *sk)
{
- return refcount_read(&sk->sk_wmem_alloc) < (sk->sk_sndbuf >> 1);
+ return refcount_read(&sk->sk_wmem_alloc) < (READ_ONCE(sk->sk_sndbuf) >> 1);
}
static inline gfp_t gfp_any(void)
diff --git a/net/core/filter.c b/net/core/filter.c
index 7deceaeeed7bace2bb805d110190b98819cfc7b1..3fed5755494bd39cf55ca1806ead67609ae8b587 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4258,7 +4258,8 @@ BPF_CALL_5(bpf_setsockopt, struct bpf_sock_ops_kern *, bpf_sock,
case SO_SNDBUF:
val = min_t(u32, val, sysctl_wmem_max);
sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
- sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
+ WRITE_ONCE(sk->sk_sndbuf,
+ max_t(int, val * 2, SOCK_MIN_SNDBUF));
break;
case SO_MAX_PACING_RATE: /* 32bit version */
if (val != ~0U)
diff --git a/net/core/sock.c b/net/core/sock.c
index 8c8f61e70141583afe52420b58fea4bcce3a74f0..cd075bc86407a5816bd448521955525ebe941694 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -785,7 +785,8 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
*/
val = min_t(int, val, INT_MAX / 2);
sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
- sk->sk_sndbuf = max_t(int, val * 2, SOCK_MIN_SNDBUF);
+ WRITE_ONCE(sk->sk_sndbuf,
+ max_t(int, val * 2, SOCK_MIN_SNDBUF));
/* Wake up sending tasks if we upped the value. */
sk->sk_write_space(sk);
break;
@@ -2089,8 +2090,10 @@ EXPORT_SYMBOL(sock_i_ino);
struct sk_buff *sock_wmalloc(struct sock *sk, unsigned long size, int force,
gfp_t priority)
{
- if (force || refcount_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf) {
+ if (force ||
+ refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf)) {
struct sk_buff *skb = alloc_skb(size, priority);
+
if (skb) {
skb_set_owner_w(skb, sk);
return skb;
@@ -2191,7 +2194,7 @@ static long sock_wait_for_wmem(struct sock *sk, long timeo)
break;
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
- if (refcount_read(&sk->sk_wmem_alloc) < sk->sk_sndbuf)
+ if (refcount_read(&sk->sk_wmem_alloc) < READ_ONCE(sk->sk_sndbuf))
break;
if (sk->sk_shutdown & SEND_SHUTDOWN)
break;
@@ -2226,7 +2229,7 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len,
if (sk->sk_shutdown & SEND_SHUTDOWN)
goto failure;
- if (sk_wmem_alloc_get(sk) < sk->sk_sndbuf)
+ if (sk_wmem_alloc_get(sk) < READ_ONCE(sk->sk_sndbuf))
break;
sk_set_bit(SOCKWQ_ASYNC_NOSPACE, sk);
@@ -2807,7 +2810,7 @@ static void sock_def_write_space(struct sock *sk)
/* Do not wake up a writer until he can make "significant"
* progress. --DaveM
*/
- if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf) {
+ if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= READ_ONCE(sk->sk_sndbuf)) {
wq = rcu_dereference(sk->sk_wq);
if (skwq_has_sleeper(wq))
wake_up_interruptible_sync_poll(&wq->wait, EPOLLOUT |
@@ -3207,7 +3210,7 @@ void sk_get_meminfo(const struct sock *sk, u32 *mem)
mem[SK_MEMINFO_RMEM_ALLOC] = sk_rmem_alloc_get(sk);
mem[SK_MEMINFO_RCVBUF] = READ_ONCE(sk->sk_rcvbuf);
mem[SK_MEMINFO_WMEM_ALLOC] = sk_wmem_alloc_get(sk);
- mem[SK_MEMINFO_SNDBUF] = sk->sk_sndbuf;
+ mem[SK_MEMINFO_SNDBUF] = READ_ONCE(sk->sk_sndbuf);
mem[SK_MEMINFO_FWD_ALLOC] = sk->sk_forward_alloc;
mem[SK_MEMINFO_WMEM_QUEUED] = sk->sk_wmem_queued;
mem[SK_MEMINFO_OPTMEM] = atomic_read(&sk->sk_omem_alloc);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index bc0481aa6633c0c871c57a89d38ef57734b51f12..11185326297211bee3746edd725d106643b78720 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -450,7 +450,7 @@ void tcp_init_sock(struct sock *sk)
icsk->icsk_sync_mss = tcp_sync_mss;
- sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[1];
+ WRITE_ONCE(sk->sk_sndbuf, sock_net(sk)->ipv4.sysctl_tcp_wmem[1]);
WRITE_ONCE(sk->sk_rcvbuf, sock_net(sk)->ipv4.sysctl_tcp_rmem[1]);
sk_sockets_allocated_inc(sk);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6995df20710a7bf48d9aca88c14e5980f4fc9615..a2e52ad7cdab3e66a469a8ca850848988b3888d7 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -359,7 +359,8 @@ static void tcp_sndbuf_expand(struct sock *sk)
sndmem *= nr_segs * per_mss;
if (sk->sk_sndbuf < sndmem)
- sk->sk_sndbuf = min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2]);
+ WRITE_ONCE(sk->sk_sndbuf,
+ min(sndmem, sock_net(sk)->ipv4.sysctl_tcp_wmem[2]));
}
/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
--
2.23.0.700.g56cf767bdb-goog
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